CHATTANOOGA, Tenn. (CNN) — Investigators say they now know what killed a 2-year-old Tennessee boy last month. They say the child overdosed on a powerful prescription pain killer. Now, the toddler’s death has been ruled a homicide.

“It’s a Schedule-2 narcotic, which means it’s got the highest abuse potential and the highest risk for overdose. So, I wouldn’t use it on kids for sure because it can kill an adult… much less a child,” said pharmacist Phillip Smith.

The drug is only prescribed to people with cancer or chronic pain after they’ve tried everything else. How one of these patches ended up on 2-year-old Demarcus Bryant’s back is unknown.

“This is one of the drugs, because it’s so serious, the FDA recommends flushing it down the toilet,” Smith said.

Now the question remains, who could have knowingly placed the patch on the child?

“Negligence. I mean, that’s just terrible if it was put on the child,” Smith said.

Demarcus was wearing a patch more than four times stronger than the weakest dosage available for an adult. The lowest dosage amount is 12 micrograms per kilogram. The highest is 100 micrograms per kilogram. For anyone under age 12, the dosage must be less than three micrograms per kilogram.

Demarcus undoubtedly felt those effects much sooner than an adult would.

“If an adult puts a patch on, it takes about eight to 12 hours to become fully effective. I would imagine it would take less than that to get into the bloodstream of a child and to do serious harm,” Smith said.